Absolute stability of axisymmetric perturbations in strongly magnetized collisionless axisymmetric accretion disk plasmas

This Letter presents a kinetic description of low-frequency and long-wavelength axisymmetric electromagnetic perturbations in nonrelativistic, strongly magnetized, and gravitationally bound axisymmetric accretion-disk plasmas in the collisionless regime. The analysis, carried out within the framework of the Vlasov-Maxwell description, relies on stationary kinetic solutions which allow for the simultaneous treatment of nonuniform fluid fields, stationary accretion flows, and temperature anisotropies. It is demonstrated that these stationary configurations are actually stable against axisymmetric kinetic instabilities of this type. As a fundamental consequence, this rules out the possibility of having the axisymmetric magnetorotational or thermal instabilities to arise in these systems.